Sheet working method, sheet working system, and various devices related to such system

ABSTRACT

An actual plate thickness and actual material constants are measured during punching before bending. The measured information is reflected on the bending, so that the bending is performed efficiently and accurately. Punching is carried out for each blank developed based on a nominal plate thickness and nominal material constants in blanking before the bending of a work W. Then, an actual plate thickness distribution and an actual material constant distribution of the work W are calculated based on various data containing a ram stroke and a pressure detected in the punching.

TECHNICAL FIELD

The present invention relates to a method and a system for processing aplate material, and various devices concerning the system, and furtherrelates to a method for calculating material attributes.

BACKGROUND ART

Conventionally, in the system for processing a plate material, a nominalvalue of a work, for example a material of SPCC, and a plate thicknessof 1.6, is entered to an automatic programming machine. Based on thisnominal value, an elongation value necessary for bending is calculated,and a developed dimension of a blank is calculated from this elongationvalue.

In blanking work before bending, punching of the blanks is carried outby a punching machine based on the developed dimension. Each blank isbent by a bending machine.

In the conventional system for processing a plate material, if acharacteristic of a work to be actually processed is far from a nominalvalue, for example if an actual plate thickness is 1.5 mm while anominal plate thickness is 1.6 mm, a correct developed length of theblank cannot be obtained at the automatic programming machine based onan elongation value generated by such a difference in plate thickness.Consequently, a problem has been inherent, i.e., an actual bentdimension after bending is not within an allowable range.

At some bending machines, a plate thickness of the work is measured by aplate thickness detecting function during bending of the work, and thismeasured plate thickness is applied to determination of a D value(stroke amount of a ram) for setting a bending angel. However, platethickness information actually measured was simply used at a singlebending machine. For example, a problem has been inherent, i.e., even ifa plate thickness of the blank is measured by the plate thicknessdetecting function during bending, the developed dimension of the blankthat has been punched cannot be corrected. Alternatively, a problem hasoccurred, i.e., correction of the blank necessitates time and labor ofreprocessing.

The work has a plate thickness changed from place to place even on asheet. Consequently, since a difference is generated in plate thicknessof each blank, as described above, a problem has been inherent, i.e., abent dimension is not within an allowable range.

Regarding the bending angle, it is known that the bending angle closerto an actual angle is obtained by calculating a spring-back amount or astroke amount based on the actual plate thickness and the actualmaterial constant rather than a nominal plate thickness and a nominalmaterial constant (tensile strength, Young's modulus, an n value, an fvalue, or the like). However, unless the actual plate thickness or theactual material constant of the work is known before bending, it cannotbe reflected on the developed dimension. Even if the material constantcan be calculated from load/stroke information during first bending,this information is reflected from next bending.

The present invention was made to solve the foregoing problems. Objectsof the invention are to provide a method for calculating materialattributes, and a method and a system for processing a plate material,which enable bending work to be carried out efficiently and accuratelyby measuring the actual plate thickness and the actual material constantduring punching before bending, and reflecting the measured informationin the bending.

DISCLOSURE OF THE INVENTION

According to an aspect of the present invention, a method is providedfor processing a plate material. The method includes punching a workinto multiple blanks, based on a nominal plate thickness and a nominalmaterial constant of the work, while detecting a ram stroke and apressure at each punching of the work into blanks. The method alsoincludes calculating an actual plate-thickness distribution and anactual material-constant distribution of the work, based on data of theram strokes and the pressures detected in the punching of the work intoblanks. The method further includes determining an actual platethickness and an actual material constant of each blank based on theactual plate-thickness distribution and the actual material-constantdistribution of the work.

According to another aspect of the present invention, the methodincludes bending each blank, based on the determined actual platethicknesses and actual material constants.

According to still another aspect of the present invention, in thebending of each blank, an elongation value of the blank is calculatedbased on the determined actual plate thickness and the actual materialconstant of the blank being bent. A determination is made as to whethera difference between the calculated elongation value and a nominalelongation value, obtained based on a nominal plate thickness and anominal material constant of the work, is within an allowable range.When the difference is within the allowable range, the bending is basedon the actual plate thickness and the actual material constant. When thedifference is outside the allowable range, the bending is stopped or asignificant part is subjected to bending based on the actual platethickness and the actual material constant.

According to an aspect of the present invention, a method is providedfor processing a plate material prior to punching a work into multipleblanks. The method includes trial-punching in gaps between adjoiningblanks, based on a nominal plate thickness and a nominal materialconstant of the work, while detecting a ram stroke and a pressure ateach trial-punching in the gaps. The method also includes calculating anactual plate-thickness distribution and an actual material-constantdistribution of the work, based on data of the ram strokes and thepressures detected in the trial-punching. The method further includesdetermining an actual plate thickness and an actual material constant ofeach blank based on the actual plate-thickness distribution and theactual material-constant distribution of the work. The methodadditionally includes blanking each blank by punching the work into themultiple blanks, based on the determined actual plate thicknesses andactual material constants. The method also includes bending each blank,based on the determined actual plate thicknesses and actual materialconstants.

According to another aspect of the present invention, in the blanking ofeach blank, an elongation value of the blank is calculated based on thedetermined actual plate thickness and actual material constant of theblank being blanked. A determination is made as to whether a differencebetween the calculated elongation value and an average elongation value,based upon an average blank having an average plate thickness andaverage material constant, is within an allowable range. When thedifference is within the allowable range, the blank is subjected toblanking based on the average plate thickness and the average materialconstant. When the difference is outside the allowable range, theblanking is stopped or the blank is subjected to blanking based on theactual plate thickness and the actual material constant.

According to still another aspect of the present invention, the bendingof each blank includes calculating an average stroke amount for anaverage blank, having an average plate thickness and average materialconstant, that is bent by a predetermined angle. A determination is madeas to whether a bend angle is within an allowable range of thepredetermined angle when another blank is bent by the calculated strokeamount. When the bend angle is within the allowable range, the blank issubjected to bending by the calculated stroke amount. When the bendangle is outside the allowable range, the bending is stopped or theblank is subjected to bending by another stroke amount calculated basedon the actual plate thickness and the actual material constant.

According to another aspect of the present invention, the bending ofeach blank includes calculating an average pinching-in angle for anaverage blank having an average plate thickness and average materialconstant by obtaining a spring-back amount for the average blank. Adetermination is made as to whether a finishing angle is within anallowable range when another blank is bent by the calculated pinching-inangle. When the finishing angle is within the allowable range, the blankis subjected to bending by the calculated pinching-in angle. When thefinishing angle is outside the allowable range, the obtained spring-backamount is utilized to calculate another pinching-in angle based on theactual plate thickness and the actual material constant, and bending iscarried out using the other calculated pinching-in angle.

A system is provided for processing a plate material. The systemincludes an automatic programming machine that calculates an expandeddimension of a blank, based on a nominal plate thickness and a nominalmaterial constant of a work to be processed. The system also includes apunching machine that punches the work into multiple blanks bycooperation of a punch with a die while detecting a ram stroke and apressure at each punching of the work into blanks. The system alsoincludes a control unit including a plate thickness/material constantarithmetic unit that calculates an actual plate-thickness distributionand an actual material-constant distribution of the work based on dataof the ram strokes and the pressures detected in the punching of thework into blanks, and that determines an actual plate thickness and anactual material constant of each blank based on the actualplate-thickness distribution and the actual material-constantdistribution of the work. The system further includes a bending machinethat bends each blank, based on the determined actual plate thicknessand the actual material constant of the blank being bent.

According to another aspect of the present invention, the control unitincludes an elongation error determiner that determines whether adifference between an elongation value of each blank, calculated basedon the determined actual plate thickness and the actual materialconstant of the blank being bent, and a nominal elongation value,obtained based on a nominal plate thickness and nominal materialconstant of the work, is within an allowable range.

According to another aspect of the present invention, the control unitincludes an elongation error determiner that determines whether adifference between an elongation value of each blank, calculated basedon the determined actual plate thickness and the actual materialconstant of the blank being bent, and an average elongation value, basedupon an average blank having an average plate thickness and averagematerial constant, is within an allowable range.

According to still another aspect of the present invention, the controlunit includes a stroke control bending error calculator that calculatesan average stroke amount for an average blank having an average platethickness and average material constant, and that determines whether abend angle is within an allowable range of a predetermined angle whenanother blank is bent by the calculated stroke amount.

According to another aspect of the present invention, the control unitincludes a pinching-in angle control bending error determiner thatcalculates a pinching-in angle by obtaining an average spring-backamount for an average blank having an average plate thickness andaverage material constant, and that determines whether a finishing angleis within an allowable range when another blank is bent by thecalculated pinching-in angle.

According to still another aspect of the present invention, the bendingof each blank includes calculating an average stroke amount for anaverage blank, having an average plate thickness and average materialconstant, that is bent by a predetermined angle. A determination is madeas to whether a bend angle is within an allowable range of thepredetermined angle when another blank is bent by the calculated strokeamount. When the bend angle is within the allowable range, the blank issubjected to bending by the calculated stroke amount. When the bendangle is outside the allowable range, the bending is stopped or theblank is subjected to bending by another stroke amount calculated basedon the actual plate thickness and the actual material constant.

According to still another aspect of the present invention, the bendingof each blank includes calculating an average pinching-in angle for anaverage blank, having an average plate thickness and average materialconstant, by obtaining a spring-back amount for the average blank. Adetermination is made as to whether a finishing angle is within anallowable range when another blank is bent by the calculated pinching-inangle. When the finishing angle is within the allowable range, the blankis subjected to bending by the calculated pinching-in angle. When thefinishing angle is outside the allowable range, the obtained spring-backamount is utilized to calculate another pinching-in angle based on theactual plate thickness and the actual material constant of the blankbeing bent, and bending is carried out using the other calculatedpinching-in angle.

In order to achieve the foregoing object, a method for calculating amaterial attribute includes the steps of: punching each of the blanksdeveloped based on a nominal plate thickness and nominal materialconstants of a work in a blanking process before bending of the work;calculating an actual plate thickness distribution and an actualmaterial constant distribution of the work based on various datacontaining a ram stroke and a pressure detected during the punchingstep; and deciding an actual plate thickness and actual materialconstants of each of the blanks based on the plate thicknessdistribution and the material constant distribution.

Thus, the actual plate thickness and the actual material constants ofeach blank can be efficiently and accurately measured during punching inblanking before bending. Therefore, this measured information can bereflected on bending, and efficient and accurate bending can be carriedout.

According to the present invention, a method for processing a platematerial includes the steps of: punching each of the blanks developedbased on a nominal plate thickness and nominal material constants of awork in blanking before bending of the work; calculating an actual platethickness distribution and an actual material constant distribution ofthe work based on various data containing a ram stroke and a pressuredetected during the punching; deciding an actual plate thickness andactual material constants of each blank based on the plate thicknessdistribution and the material constant distribution; and bending each ofthe blanks based on the actual plate thickness and the actual materialconstants.

Thus, the actual plate thickness and the actual material constants ofeach blank can be measured during punching in blanking before bending.Therefore, this measured information can be reflected on bending, andefficient and accurate bending can be carried out. Moreover, forexample, a block of blanks having small bending errors simplifies workin inspection time. Thus, the inspection time after bending can beshortened.

According to the present invention, in the method for processing a platematerial, in the bending of each of the blanks, an elongation value ofeach of the blanks is calculated based on the actual plate thickness andthe actual material constants thereof, determination is made as towhether a difference between this elongation value and an elongationvalue obtained based on the nominal plate thickness and the nominalmaterial constants of the work is within an allowable range or not, theblank having the difference within the allowable range is subjected tobending based on the actual plate thickness and the actual materialconstants, and for the blank having the difference outside the allowablerange, a significant dimension part thereof is preferentially subjectedto bending based on the actual plate thickness and the actual materialconstants, or the bending is stopped.

Thus, an elongation error of each blank can be measured beforehand.Therefore, since bending along an actual situation can be carried outdepending on whether the elongation error is within the allowable rangeor not, it is possible to improve product accuracy and work efficiencyafter bending, and shorten the inspection time after bending.

According to the present invention, a method for processing a platematerial includes the steps of: executing trial-punching on a gapbetween blanks developed based on a nominal plate thickness and nominalmaterial constants of a work in a blanking process before bending of thework; calculating an actual plate thickness distribution and an actualmaterial constant distribution of the work based on various datacontaining a ram stroke and a pressure detected during thetrial-punching; deciding an actual plate thickness and actual materialconstants of each of the blanks blank based on the plate thicknessdistribution and the material constant distribution; developing each ofthe blanks and executing blanking based on the actual plate thicknessand the actual material constants; and bending each of the blanks basedon the actual plate thickness and the actual material constants.

Thus, since the actual plate thickness distribution and the materialconstant distribution of the work can be measured during trial-punchingbefore bending, an actual plate thickness and actual material constantsof each blank can be decided. Since this measured information can bereflected on accurate development and blanking of each blank and alsoreflected on bending, efficient and accurate bending can be carried out.Moreover, for example since a block of blanks having small bendingerrors simplifies work in the inspection time, it is possible to shortenthe inspection time after bending.

According to the present invention, in the method for processing a platematerial, in the blanking of each of the blanks, an elongation value ofeach of the blanks is calculated based on the actual plate thickness andthe actual material constants thereof, determination is made as towhether a difference between this elongation value and an averageelongation value obtained from the blank having an average platethickness and average material constants among the blanks is within anallowable range or not, the blank having the difference within theallowable range is developed and subjected to blanking based on theaverage plate thickness and the average material constants, and theblank having the difference outside the allowable range is developed andsubjected to blanking based on the actual plate thickness and the actualmaterial constants or the blanking thereof is stopped.

Thus, since an elongation error of each blank can be calculatedbeforehand, blanking and bending along an actual situation can becarried out depending on whether the elongation error is within theallowable range or not. Therefore, it is possible to improve productaccuracy and work efficiency during bending, and shorten the inspectiontime after bending.

According to the present invention, in the method for processing a platematerial, in the bending of each of the blanks, an stroke amount whenthe blank having an average plate thickness and average materialconstants among the blanks is bent by a predetermined angle iscalculated, determination is made as to whether an angle when anotherblank is bent by the same stroke amount is within an allowable range ornot with respect to the predetermined angle, the blank having the anglewithin the allowable range is subjected to bending by the same strokeamount, and the blank outside the allowable range is subjected tobending by a stroke amount calculated based on plate thickness andmaterial constants thereof or the bending step is stopped.

Thus, since a bending error under control of the stroke amount of eachblank can be calculated beforehand, blanking and bending along an actualsituation can be carried out depending on whether the bending error iswithin the allowable range or not. Therefore, product accuracy and workefficiency during bending are improved, and the inspection time afterbending is shortened.

According to the present invention, in the method for processing a platematerial, in the bending of each blank, a pinching-in angle iscalculated by obtaining a spring-back amount of the blank having theaverage plate thickness and the average material constants among theblanks, determination is made as to whether a finishing angle afteranother blank is bent by the same pinching-in angle is within anallowable range or not, the blank having the finishing angle within theallowable range is subjected to bending by the same pinching-in angle,for the blank having the finishing angle outside the allowable range,the spring-back amount is obtained to calculate the pinching-in anglebased on the plate thickness and the material constants thereof, andbending is carried out by the pinching-in angle.

Thus, a bending error under control of the pinching-in angle of eachblank can be calculated beforehand. Therefore, since blanking andbending along an actual situation can be carried out depending onwhether the bending error is within the allowable range or not, productaccuracy and work efficiency during bending are improved, and theinspection time after bending is shortened.

According to the present invention, a system for processing a platematerial includes: an automatic programming machine for developingblanks based on a plate thickness and material constants of a work; apunching machine for punching and blanking the work by cooperationbetween a punch and a die; a control unit including a platethickness/material constant arithmetic unit for calculating an actualplate thickness distribution and an actual material constantdistribution based on various data containing a ram stroke and apressure detected during the punching of the work by the punchingmachine, and deciding an actual plate thickness and actual materialconstants of each of the blanks from the calculated plate thicknessdistribution and material constant distribution; and a bending machinefor bending each of the blanks based on the actual plate thickness andthe actual material constants thereof.

Thus, since the actual plate thickness distribution and the materialconstant distribution of the work can be measured during punching beforebending, the actual plate thickness and the actual material constants ofeach blank can be decided. Since this measured information can bereflected on accurate development and blanking of each blank and alsoreflected on bending, efficient and accurate bending can be carried out.Moreover, for example since a block of blanks having small bendingerrors simplifies work in the inspection time, the inspection time afterbending is shortened.

According to the present invention, in the system for processing a platematerial, the control unit includes elongation error determining meansfor determining whether a difference between an elongation value of eachof the blanks calculated based on the actual plate thickness and theactual material constants of each of the blanks and an elongation valueobtained from a nominal plate thickness and nominal material constantsof a work is within an allowable range or not.

Thus, since the elongation error of each blank can be calculatedbeforehand, bending along an actual situation can be carried outdepending on whether the elongation error is within the allowable rangeor not. Therefore, product accuracy and work efficiency during bendingare improved, and the inspection time after bending is shortened.

According to the present invention, in the system for processing a platematerial, the control unit includes elongation error determining meansfor determining whether a difference between an elongation value of eachof the blanks obtained based on the actual plate thickness and theactual material constants thereof and an average elongation valueobtained from the blank having an average plate thickness and averagematerial constants among the blanks is within an allowable range or not.

Thus, since the elongation error of each blank can be calculatedbeforehand, blanking and bending along an actual situation can becarried out depending on whether the elongation error is within theallowable range or not. Therefore, product accuracy and work efficiencyduring bending are improved, and the inspection time after bending isshortened.

According to the present invention, in the system for processing a platematerial, the control unit includes stroke control bending errordetermining means for calculating a stroke amount when the blank havingan average plate thickness and average material constants among theblanks based on the actual plate thickness and the actual materialconstants, and determining whether an angle when another blank is bentby the same stroke amount is within an allowable range or not withrespect to a predetermined angle.

Thus, since a bending error under control of the stroke amount of eachblank can be calculated beforehand, blanking and bending along an actualsituation can be carried out depending on whether the bending error iswithin the allowable range or not. Therefore, product accuracy and workefficiency during bending are improved, and the inspection time afterbending is shortened.

According to the present invention, in the system for processing a platematerial, the control unit includes pinching-in angle control bendingerror determining means for calculating a pinching-in angle by obtaininga spring-back amount of the blank having an average plate thickness andan average material constants among the blanks, and determining whethera finishing angle after another blank is bent by the same pinching-inangle is within an allowable range or not.

Thus, since a bending error under control of the pinching-in angle ofeach blank can be calculated beforehand, blanking and bending along anactual situation are carried out depending on whether the bending erroris within the allowable range or not. Thus, product accuracy and workefficiency during bending are improved, and the inspection time afterbending is shortened.

According to the present invention, a method for processing sheet metalincludes the steps of: processing and forming a sample and a blank on awork while leaving a microjoint part in a blanking process; detecting atleast one of a plate thickness of the work in an optional position and aspring-back amount during bending of the sample; transmittinginformation of at least one of the plate thickness and the spring-backamount to a control unit of a bending machine in a bending process afterthe blanking process; and carrying out bending by calculating a ramcontrol value in bending by using data of at least one of thetransmitted plate thickness and spring-back amount, and other bendingdata.

Thus, in a blank processing step such as punching or laser cuttingbefore the bending step, at least one of the plate thickness and thespring-back amount of the work is detected as quantitative data of amaterial characteristic necessary for bending simultaneously with blankprocessing. Since at least one of the plate thickness and thespring-back amount of the work is incorporated as a control parameter inbending control at a stage of bending using a press brake, it ispossible to obtain a bent product having a target bending angle fromfirst processing without carrying out trial bending.

According to the present invention, a system for processing sheet metalincludes: a blank processing machine capable of processing and forming asample and a blank on a work while leaving a microjoint part, the blankprocessing machine including a work characteristic detection unit fordetecting at least one of a plate thickness of the work in an optionalposition and a spring-back amount during bending of the sample inbending; and a bending machine for carrying out bending by calculating aram control value in bending by using at least one data of the platethickness and the spring-back amount of the work and the spring-backamount detected by the work characteristic detection unit provided inthe blank processing machine, and other bending data.

Thus, at the blank processing step carrying out punching or lasercutting before bending, at least one of the plate thickness and thespring-back amount of a work is detected as quantitative data of amaterial characteristic necessary for bending simultaneously with blankprocessing. Therefore, since at least one of the plate thickness and thespring-back amount of the work is incorporated as a control parameter inbending control at the stage of bending using a press brake, it ispossible to obtain a bent product having a target bending angle fromfirst processing without carrying out trial bending.

According to the present invention, a blank processing machine capableof processing and forming a sample and a blank on a work while leaving amicrojoint part, the blank processing machine including a workcharacteristic detection unit for detecting at least one of a platethickness of the work in an optional position and a spring-back amountduring bending of the sample in bending.

Thus, at the blank processing machine, at least one of the platethickness and the spring-back amount of the work can be detected asquantitative data of a material characteristic necessary for bendingsimultaneously with blank processing in the step before bending.Therefore, at least one of the plate thickness and the spring-backamount of the work is used as a control parameter at the stage ofbending.

According to the present invention, in the blank processing machine, thework characteristic detection unit is a work plate thickness measuringdevice including: a probe member provided to be freely moved up anddown, the probe member being capable of bending the sample of the workin cooperation with a die; a sensor plate provided to be freely moved upand down relative to the probe member, and provided to be always presseddownward to be protruded downward by a predetermined length from a lowerend of the probe member; position detecting means for detecting adifference in relative positions of a vertical direction between theprobe member and the sensor plate; and a plate thickness arithmetic unitfor calculating a plate thickness of the work based on referenceposition information by the position detecting means when tips of theprobe member and the sensor plate coincide with each other inmeasurement of a known reference plate thickness and measuring positioninformation by the position detecting means when the tips of the probemember and the sensor plate coincide with each other in plate thicknessmeasurement of the work.

Thus, a probe member is started to be lowered to a work set in apredetermined position, and first, a sensor plate is brought intocontact with the work. Then, the probe member is brought into contactwith the work while the sensor plate is in contact with the work. Whentips of the probe member and the sensor plate coincide with each other,the measuring position information is detected by the position detectingmeans. The reference position information is detected by the positiondetecting means when the tips of the probe and the sensor plate coincidewith each other in previous measurement of a known reference platethickness. Accordingly, the plate thickness of each of the sample andthe blank is calculated based on a difference between the measuredposition information and the reference position information.

According to the present invention, in the blank processing machine, thework characteristic detection unit is a spring-back arithmetic unitincluding: a probe member provided to be freely moved up and down, theprobe member being capable of bending the sample of the work bycooperation with a die; a sensor plate provided to be freely moved upand down relative to the probe member, and provided to be always presseddownward to be protruded downward by a predetermined length from a lowerend of the probe member and freely brought into contact with both sidefaces inside the work during bending; position detecting means fordetecting a difference in relative positions of a vertical directionbetween the probe member and the sensor plate; and a spring-backarithmetic unit for calculating a spring-back amount of the sample basedon a difference between bending position information of the probe memberand the sensor plate by the position detecting means at a predeterminedstroke of the probe member and spring-back position information of theprobe member and the sensor plate by the position detecting means whenthe probe member is separated from the sample and the sample is sprungback.

Thus, the bending position information is detected by the positiondetecting means when the probe member is lowered by a predeterminedstroke to bend the sample. Then, the spring-back position information isdetected by the position detecting means when the probe member isseparated from the sample, and the sample is sprung back. Thespring-back amount of the sample is calculated based on a differencebetween the spring-back position information and the bending positioninformation.

According to the present invention, a work plate thickness measuringdevice includes: a probe member provided to be freely moved up and down,the probe member being capable of bending a sample of a work incooperation with a die; a sensor plate provided to be freely moved upand down relative to the probe member, and provided to be always presseddownward to be protruded downward by a predetermined length from a lowerend of the probe member; position detecting means for detecting adifference in relative positions of a vertical direction between theprobe member and the sensor plate; and a plate thickness arithmetic unitfor calculating a plate thickness of the work based on referenceposition information by the position detecting means when tips of theprobe member and the sensor plate coincide with each other inmeasurement of a known reference plate thickness and measuring positioninformation by the position detecting means when the tips of the probemember and the sensor plate coincide with each other in the platethickness measurement of the work.

Thus, the probe member is started to be lowered to the work set in apredetermined position, and first, the sensor plate is brought intocontact with the work. Then, the probe member is brought into contactwith the work while the sensor plate is in contact with the work. Whentips of the probe member and the sensor plate coincide with each other,the measuring position information is detected by the position detectingmeans. The reference position information is detected by the positiondetecting means when the tips of the probe and the sensor plate coincidewith each other in previous measurement of a known reference platethickness. Accordingly, the plate thickness of each of the sample andthe blank is calculated based on a difference between the referenceposition information and the measuring position information.

According to the present invention, a spring-back measuring deviceincludes: a probe member provided to be freely moved up and down, theprobe member being capable of bending a sample of a work in cooperationwith a die; a sensor plate provided to be freely moved up and downrelative to the probe member, and provided to be always pressed downwardto be protruded downward by a predetermined length from a lower end ofthe probe member and freely brought into contact with both side facesinside the work during bending; position detecting means for detecting adifference in relative positions of a vertical direction between theprobe member and the sensor plate; and a spring-back arithmetic unit forcalculating a spring-back amount of the sample based on a differencebetween bending position information of the probe member and the sensorplate by the position detecting means at predetermine stroke of theprobe member, and spring-back position information of the probe memberand the sensor plate by the position detecting means when the probemember is separated from the sample and the sample is sprung back.

Thus, the bending position information when the probe member is loweredby a predetermined stroke to bend the sample is detected by the positiondetecting means. Then, the spring-back position information is detectedby the position detecting means when the probe member is separated fromthe sample and the sample is sprung back. The spring-back amount of thesample is calculated based on a difference between the bending positioninformation and the bending position information.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory front view schematically showing each deviceused in a plate material processing system according to an embodiment ofthe present invention.

FIG. 2 is a block diagram showing a control unit of a punching machineaccording to the embodiment of the present invention.

FIG. 3 is a stroke/load diagram in punching according to the embodimentof the present invention.

FIG. 4 is an expanded side view showing a measurement indicator portionof a bending machine shown in FIG. 1 according to the embodiment of thepresent invention.

FIG. 5 is a sectional view showing an internal configuration of adetection head according to the embodiment of the present invention.

FIG. 6 is a block diagram showing a control unit of the bending machine(press brake) according to the embodiment of the present invention.

FIG. 7 is a flowchart showing a first embodiment of the presentinvention.

FIG. 8 is a development elevation showing a blank layout of each blankon a work sheet according to the first embodiment.

FIG. 9 is a view showing a plate thickness distribution on the worksheet according to the first embodiment.

FIG. 10 is an explanatory view showing an “elongation error” accordingto the first embodiment.

FIG. 11 is an explanatory view showing a “D value control bending error”according to the first embodiment.

FIG. 12 is an explanatory view showing a “pinching-in angle controlbending error” according to the first embodiment.

FIG. 13 is an explanatory view showing a display state of a messageaccording to the first embodiment.

FIG. 14 is a flowchart showing a second embodiment of the presentinvention.

FIG. 15 is a blanking development elevation of a waste hole and eachblank on a work sheet according to the second embodiment.

FIG. 16 is a view showing a punching state of the waste hole on the worksheet according to the second embodiment.

FIG. 17 is an explanatory view showing a position of a test piece on thework sheet according to the second embodiment.

FIG. 18 is an explanatory view schematically showing a sheet metalprocessing system according to a third embodiment.

FIG. 19 is a plan view showing an example of a blank according to thethird embodiment.

FIG. 20 is an explanatory view showing in detail a sample material ofFIG. 19.

FIG. 21 is an explanatory view schematically showing a workcharacteristic detecting unit according to the embodiment of the presentinvention.

FIG. 22 is a view showing a right side of FIG. 21.

FIGS. 23A and 23B are front views respectively showing a bending stateand a spring-back state of the sample materials.

FIG. 24 is a graph showing an amount of displacement of a sensor platein plate thickness and spring-back amount measurement.

FIG. 25 is a table showing array data of a measured plate thickness, aspring-back amount ε, a die condition used for bending, and the like.

BEST MODES FOR CARRYING OUT THE INVENTION

Next, description will be made of preferred embodiments of a method anda system for processing a plate material according to the presentinvention with reference to the accompanying drawings.

Referring to FIG. 1, a system of an embodiment for processing a platematerial includes an automatic programming machine 1 for developingblanks based on a plate thickness, and material constant (tensilestrength, Young's modulus, an n value, an f value or the like) of a workW, for example a turret punch press 3 as a punching machine for punchingthe work W by cooperative work between a punch P and a die D forblanking, and for example a press brake 5 as a bending machine forbending each blank punched by the turret punch press 3.

More specifically, for example, the above-described turret punch press 3as the punching machine is formed in a frame structure, where both sidesof an upper frame 13 are supported on side frames 9 and 11 erected onboth sides of a base 7. Below the upper frame 13, a disk-shaped upperturret 15 is rotatably loaded, which includes a variety of punches P tobe freely detached and exchanged. A lower turret 17 facing the upperturret 15 is rotatably loaded on an upper surface of the base 7. Thislower turret 17 includes a number of dies D facing the variety ofpunches P, which are disposed in a circular-arc shape and loaded to befreely detached and exchanged. The upper and lower turrets 15 and 17 arerotated in synchronization in the same direction by control of a controlunit 19.

Positions of dies D and punches P loaded on the right side of the upperand lower turrets 15 and 17 in FIG. 1 are processing positions. Astriker 21 is installed so as to be freely moved up and down on theupper frame 13 above the punches P located in the processing positions.This striker 21 is connected through, for example a ram 29 (punch pressmember), to a piston rod 27 of a piston 25 moved up and down in ahydraulic cylinder 23 as a drive unit provided in the upper frame 13.

The turret punch press 3 also includes a work movement positioningdevice 31 for moving the work W back and forth, and left and right andpositioning the work W to the processing position. The movementpositioning device 31 is provided so as to be controlled by the controlunit 19. The work movement positioning device 31A includes a carriagebase 33 provided on the base 7 so as to be freely moved in a Y axisdirection of a left-and-right direction in FIG. 1. On this carriage base33, a carriage 35 is provided so as to be freely moved in an X axisdirection orthogonal to the Y axis substantially on a plane. Thecarriage 35 includes a plurality of work clamps 37 provided at properintervals in the X axis direction to clamp the work W.

Accordingly, the punch P is struck by the ram 29, and the work W set inthe processing position is subjected to punching by cooperation betweenthe punch P and the die D.

As shown in FIG. 2, the control unit 19 of the turret punch press 3includes a plate thickness/material constant arithmetic unit, forexample a plate thickness/material constant detection unit 39, forcalculating an actual plate thickness distribution and an actualmaterial constant distribution of the work W based on various datacontaining a ram stroke and a pressure detected in punching of the workW, and deciding an actual plate thickness and actual material constantsof each blank from the calculated plate thickness distribution and thecalculated material constant distribution.

Referring to FIG. 2, an encoder 41 is provided below the hydrauliccylinder 23. This encoder 41 outputs a pulse signal proportional to amoving speed following an up-and-down movement of the ram 29. The pulsesignal is entered to a position detection unit 43, where a lower endposition of the punch P, i.e., a stoke amount of the ram 29, isdetected. The stroke amount is electrically transmitted to the platethickness/material constant detection unit 39 for detecting the platethickness and the material constants of the work W.

A servo valve 53 is communicated through a pressure side hydraulic pipeline 47 to a pressure chamber 45 of the hydraulic cylinder 23, and iscommunicated through a back-pressure side hydraulic pipe line 51 to aback-pressure chamber 49. A command is issued from a main control unit55 to switch the servo valve 53, and pressure oil of a hydraulic pump 57is accordingly supplied to the pressure chamber 45 or the back-pressurechamber 49 of the hydraulic cylinder 23. Thus, the ram 29 is driven upand down at a predetermined speed.

A pressure sensor 59 for detecting a pressing force in punching isconnected to the pressure side hydraulic pipe line 47. The pressingforce detected by this pressures sensor 59 is electrically transmittedto the plate thickness/material constant detection unit 39.

With the foregoing configuration, at the plate thickness/materialconstant detection unit 39, a stroke/load diagram as shown in FIG. 3 isobtained from the stroke amount transmitted from the position detectionunit 43 and a punching load transmitted from the pressure sensor 59 inpunching of the work W. In FIG. 3, a reference code B denotes an elasticdeformation area, C a plastic deformation area, a Cmax a maximumpunching load, and D breaking.

As shown in the stroke/load diagram, a load is suddenly increased at aposition of a point A, where the punch P is brought into contact withthe work W, so that the position of the point A is detected.Accordingly, the actual plate thickness is detected.

Also, the material constants are obtained from the stroke/load diagram.For example, a tensile strength is obtained from a size of the maximumpunching load Cmax. Alternatively, Yung's modulus E is obtained frominclination of the elastic deformation area B, and yield stress σ, an Nvalue, an F value, a maximum tensile stress value and the like areobtained from the plastic deformation area C.

More specifically, the material constants in punching cannot be directlyused for calculation in bending. However, since the stroke/load diagramsof similar shapes are obtained in the cases of punching and applyingtension using the same material, the material constants obtained fromthe stroke/load diagram of punching can be converted into the materialconstants in the case of applying tension.

For example, it is assumed that the material constants calculated fromthe stroke-load diagram obtained from a tensile test of a referencematerial are Young's modulus E0T, Poisson's ratio ν0T, yield stress σ0T,an N value n0T, and an F value f0T. These material constants in thetension application are stored beforehand in a memory 61 of the controlunit 19 of the turret punch press 3.

It is assumed that the material constants calculated from thestroke/load diagram obtained by punching the reference material with areference die for material constant detection as described above areYoung's modulus E0P, Poisson's ratio νoP, yield stress σ0P, an N valuen0P, and an F value f0P. These material constants in punching are alsostored beforehand in the memory 61 of the control unit 19 of the turretpunch press 3.

Assuming that the material constants calculated from the stroke/loaddiagram obtained by punching the actually used work W with the referencedie for material constant detection as described above are Young'smodulus E1P, Poisson's ratio ν1P, yield stress σ1P, an N value n1P, andan F value f1P, the material constants in tension application of theactually used work W are converted into Young's modulus E1T[=(E1P/E0P)E0T], Poisson's ratio ν1T [=(ν1P/ν0P)ν0T], yield stress σ1T[=(σ1P/σ0P)σ0T], an N value n1T [=(n1P/n0P)n0T], and an F value f1T[=(f1P/f0P)f0T].

Referring back to FIG. 2, the control unit 19 of the turret punch press3 includes the memory 61 for storing data from the automatic programmingmachine 1, and data of the stroke/load diagram or the plate thicknessdistribution and the material constant distribution obtained by theplate thickness/material constant detection unit 39.

Further, the control unit 19 includes error determining means, forexample, an elongation error determination unit 63, for determiningwhether a difference between an elongation value of each blankcalculated based on the actual plate thickness and material constants ofeach blank decided by the plate thickness/material constant detectionunit 39, and an elongation value obtained from the nominal platethickness and the nominal material constants of the work W is within anallowable range or not.

At the elongation error determination unit 63, determination can also bemade as to whether a difference between the elongation value of eachblank calculated based on the actual plate thickness and materialconstants of each blank decided by the plate thickness/material constantdetection unit 39, and an average elongation value obtained from theblank having the average plate thickness and the average materialconstants among the banks is within an allowable range or not.

The control unit 19 includes stroke control bending error determiningmeans, for example, a D value bending error determination unit 65, forcalculating a stroke amount when the blank having the average platethickness and the average material constants is bent by a predeterminedangle among the blanks based on the actual plate thickness and theactual material constants, and determining whether an angle when anotherblank is bent by the same stroke amount is within an allowable range ornot with respect to a predetermined angle.

The control unit 19 includes pinching-in angle control bending errordetermining means, for example, a pinching-in angle bending errordetermination unit 67, for calculating a pinching-in angle by obtaininga spring-back amount of the blank having the average plate thickness andmaterial constants among the blanks, and determining whether a finishingangle after the other blank is bent to the same pinching-in angle iswithin an allowable range or not.

Referring back to FIG. 1, the bending machine, for example the pressbrake 5, includes erected C frames 69L and 69R. A lower table 71 isprovided at the lower front face of the C frames 69L and 69R so as to bemoved up and down. A die D is detachably loaded on the lower table 71.On the other hand, an upper table 73 is fixed on the upper front face ofthe C frame 69. On the lower portion of this upper table 73, a punch Pis detachably loaded.

Main cylinders 75L and 75R are provided below the C frame 69. Tips(upper ends) of piston rods 77L and 77R loaded on the main cylinders 75Land 75R are attached to the lower table 71. Crowning sub-cylinders 79Land 79R are incorporated in the lower table 71 and attached throughpiston rods 81L and 81R to an upper portion of the lower table 71.

Pressure reducing valves 83L and 83R are respectively connected to themain cylinder 75L and the sub-cylinder 79L, and to the main cylinder 75Rand the sub-cylinder 79R. Pressure sensors 85L and 85R are respectivelyconnected to the main cylinders 75L and 75R. Position scales 87L and 87Rare provided on both side faces of the upper table 73. Position sensors91L and 91R are provided through brackets 89L and 89R on both side facesof the lower table 71.

Further, a guide rail 93 is laid on the upper front face of the lowertable 71. On this guide rail 93, a bending angle measuring device 95 fordetecting a bending angle when the work W is bent is provided so as tobe moved left and right.

The bending angle measuring device 95, the pressure sensors 85L and 85R,and the position sensors 91L and 91R are respectively connected to thecontrol unit 97.

Referring to FIG. 4, on the guide rail 93, a slider 99 is provided so asto be freely moved and positioned in a direction orthogonal to a papersurface of FIG. 4. A bracket 101 is attached to the slider 99 by aplurality of bolts. A guide rail 103 is provided back and forth (leftand right in FIG. 4) on the bracket 101. A slider 105 is provided so asto be moved back and forth along the guide rail 103. A measurementindicator 107 is provided on the slider 105.

The measurement indicator 107 includes a detection head 109, which issupported so as to be rotated integrally with a gear 111 having arotational center P0 on the front center of the detection head 109. Inaddition, a worm gear 113 to be engaged with the gear 111 is rotatablyprovided. The worm gear 113 is rotary-driven by a motor 115.

Thus, when the motor 115 rotates the worm gear 113, the gear 111 engagedwith the worm gear 113 is rotary-driven. Accordingly, the detection head109 is swung up and down (up-and-down direction in FIG. 4) by a desiredangle around the front center.

Referring to FIG. 5, the detection head 109 includes a laser projector117 as a light emitting element on its center, and first and secondphoto acceptance units 119A and 119B made of, for example photodiodes,respectively provided above and below the laser projector 117.

By referring to FIG. 5, description is now made of a case of detecting abending angle 2·θ of the work W by using the detection head 109. A laserbeam LB emitted from the laser projector 117 of the swinging detectionhead 109 is reflected on a surface of the work W, received by the firstand second photo acceptance units 119A and 119B, then converted into asignal and transmitted to the control unit 97. That is, the control unit97 detects that when rotation is made up to a position where an angle ofthe detection head 109 reaches θ1, the laser beam LB emitted from thelaser projector 117 is reflected on the work W, and a quantity of thereflected light received by the first photo acceptance unit 119A becomesmaximum.

For example, regarding a change in a quantity of received reflectedlight with respect to a rotational angle of the detection head 109,generally, a quantity of received light by the first photo acceptanceunit 119A becomes maximum when the detection head is rotatedcounterclockwise by an angle θ1 with respect to a reference angle θ (θ=0in the example shown in FIG. 5). A quantity of received light by thesecond photo acceptance unit 119B becomes maximum when the detectionhead 109 is rotated clockwise by an angle θ2 with respect to thereference angle θ.

The first and second photo acceptance units 119A and 119B are providedat equal distances from the laser projector 117. Accordingly, it can beunderstood that in an intermediate position between the angles of thedetection head 109 when the quantities of light received by the firstand second photo acceptance units 119A and 119B respectively becomemaximum, a laser beam LB from the laser projector 117 is projectedperpendicularly to the bent work W. Thus, an angle 2θ of the bent work Wis obtained by 2·θ=θ1+θ2.

Referring to FIG. 6, the control unit 97 of the press brake 5 includes aCPU 121. An input unit 123 such as a keyboard for entering various data,and a display unit 125 such as a CRT for displaying various data areconnected to the CPU 121. In addition, the main cylinders 75L and 75R,the pressure sensors 59L and 59R, the position sensors 91L and 91R, andthe measurement indicator 107 are connected to the CPU 121.

A memory 127 is connected to the CPU 121. This memory 127 receives andstores data entered from the input unit 123 regarding die conditionsincluding a punch tip are PR, a punch tip angle PA, a punch tip slopelength PL, a punch bending constant PT, a die shoulder radius DR, a diegroove angle DA, and a die V width V, and material conditions includinga material, a plate thickness T, a bending length B, and a frictioncoefficient.

The memory 127 is constructed to fetch in and store the actual platethickness and material constants of each blank calculated by the platethickness/material constant detection unit 39 of the control unit 19 ofthe turret punch press 3, the results determined by the elongation errordetermination unit 63, the D value bending error determination unit 65and the pinching-in angle bending error determination unit 67, and dataobtained when determination is made by each of the determination units63, 65 and 67, for example an elongation value, a stroke amount, aspring-back amount, a pinching-in angle and the like of each blankcalculated based on the actual plate thickness and material constants ofeach blank, which are electrically transmitted from the control unit 19of the turret punch press 3.

Further, an arithmetic unit 129 is connected to the CPU 121, whichcalculates a proper bending condition of each blank based on the dataelectrically transmitted from the control unit 19 of the turret punchpress 3. A comparison determination unit 131 is also connected to theCPU 121, which issues a command for comparing the proper bendingcondition of each blank calculated by the arithmetic unit 129 with theactual bending load, the actual stroke amount and the actual pinching-inangle detected by the pressure sensors 59L and 59R, the position sensors91L and 91R, and the measurement indicator 107 for each bending workcarried out by an optional angle at the press brake 5 and for thusperforming proper bending.

In the described embodiment, the elongation error determination unit 63,the D value bending error determination unit 65, and the pinching-inangle bending error determination unit 67 are provided in the controlunit 19 of the turret punch press 3. However, these components may beprovided in the control unit 97 of the press brake 5.

Next, description will be made of a plate material processing methodusing the plate material processing system constructed in the foregoingmanner according to the first embodiment.

Referring to FIG. 7, the automatic programming machine 1 receives entryof data including the nominal plate thickness and the nominal materialconstants (tensile strength, Young's modulus, n value, f value, and thelike) of the work W.

The elongation value of each blank is calculated based on these nominalplate thickness and material constants, and then developed dimensionsare calculated. For the work W, a blank layout of each blank in the workW is decided as shown in FIG. 8 (steps S1 and S2).

A processing program containing development data of each blank istransmitted to the control unit 97 of the turret punch press 3 as shownin FIG. 1. At the turret punch press 3, each blank is subjected toactual punching based on the processing program, thereby carrying outblanking.

At the plate thickness/material constant detection unit 39 of thecontrol unit 19, as described above, each time when each blank issubjected to punching, various data containing the ram stroke and thepressure are detected, and the plate thickness and the materialconstants such as a tensile strength in each punching position arecalculated based on the stroke value and a load. Thus, the actual platethickness distribution and the material constant distribution of thework W are calculated, for example as shown in FIG. 9.

Therefore, the actual plate thickness and the material constants of eachblank are decided from the above-described plate thickness and materialconstant distributions. When each blank is subjected to punching, ablank identification code, the plate thickness, the tensile strength andthe like may be simultaneously marked. For example, on each blank, aplate thickness t of 0.8 mm, a tensile strength of 2.94×10⁸ Pa (30kg/mm²), an identification code (A), (B), (C) or the like can be writtendown (step S3).

Among the blanks, a particular blank having the average plate thicknessand the average tensile strength is extracted. For example, assumingthat among three blanks, a blank (A) has a plate thickness t of 0.80 mmand a tensile strength of 2.94×10⁸ Pa (30 kg/mm²), a blank (B) has aplate thickness t of 0.81 mm and a tensile strength of 3.04×10⁸ Pa (31kg/mm²), and a blank (C) has a plate thickness t of 0.82 mm and atensile strength of 3.14×10⁸ Pa (32 kg/mm²), the blank (B) is theparticular average blank (step S4) among these blanks.

Then, at the control unit 19, at least one of the following threebending errors is predicted based on the above-described actual platethickness and material constants of each blank (step S5).

1. An elongation error of each blank is calculated based on the nominalplate thickness and the nominal material constants.

2. A bending error of each blank under D value control is calculatedbased on the actual plate thickness and the actual material constants ofeach blank.

3. A bending error of each blank under pinching-in angle is calculatedbased on the actual plate thickness and the actual material constants ofeach blank.

The “1. elongation error of each blank” is now explained more in detail.At the plate thickness/material constant detection unit 39 of thecontrol unit 19, the elongation value of each blank is calculated basedon the actual plate thickness and the actual material constants of eachblank. A difference between this elongation value of each blank and theelongation value obtained based on the nominal plate thickness and thenominal material constants of the work W becomes the “elongation error”.

The elongation value is obtained from the plate thickness and thematerial of each blank [elongation value=f (plate thickness, material,and die V width)].

For example, as shown in FIG. 10, for the blank (A), the elongationvalue is calculated at 1.11 mm based on a plate thickness t of 1.16 mmand a tensile strength σA. For the blank (B), the elongation value iscalculated at 1.12 mm based on a plate thickness t of 1.17 mm and atensile strength σB. For the blank (C), the elongation value iscalculated at 1.13 mm based on a plate thickness t of 1.18 mm and atensile strength σC.

The elongation value calculated based on the nominal plate thickness andthe nominal material constants by the automatic programming machine 1 instep S1 has been entered to the memory 61 of the control unit 19. Forexample, if the elongation value calculated from a nominal platethickness t of 1.20 mm and a tensile strength σ0 is 1.20 mm, adifference between the actual elongation value of each blank and thiselongation value of 1.20 mm becomes the “elongation error”.

Thus, the elongation errors are respectively calculated to be 0.09 mm,0.08 mm, and 0.07 mm for the blanks (A), (B) and (C).

The “2. bending error of each blank under D value control” is nowexplained more in detail. At the plate thickness/material constantdetection unit 39 of the control unit 19, the D value (stroke amount)when the blank having the average plate thickness and the averagematerial constants among the blanks is bent by a predetermined angle iscalculated based on the actual plate thickness and the actual materialconstants. A difference between an angle of another blank bent by thesame stroke amount and the predetermined angle becomes the “D valuecontrol bending error”.

For example, as shown in FIG. 11, the D value when the blank (B) havingthe average plate thickness and the average material constants is bentby a predetermined angle 90° is calculated based on the actual platethickness and the actual material constants of the blank (B). Thiscalculated D value is now assumed to be 2.10.

For the other blanks (A) and (C), the bending angles with the D valueequal to the calculated D value of the blank (B) are calculated based onthe actual plate thickness and the actual material constants of theindividual blanks (A) and (C). As a result, since the bending angle ofthe blank (A) is 90.5°, the bending error is 0.5°. Since the bendingangle of the blank (C) is 89.5°, the bending error is 0.5°.

The “3. bending error of each blank under pinching-in angle control” isnow explained more in detail. At the plate thickness/material constantdetection unit 39 of the control unit 19, the spring-back amount of theblank having the average plate thickness and the average materialconstants among the blanks is calculated based on the actual platethickness and the actual material constants. From this spring-backamount, the pinching-in angle is calculated for achieving apredetermined finishing angle. The finishing angle after another blankis bent to the similar pinching-in angle is calculated based on theindividual actual plate thickness and material constants. A differencebetween the finishing angle when another blank is bent to the similarpinching-in angle and the above-described predetermined angle becomesthe “pinching-in angle control bending error”.

For example, as shown in FIG. 12, since the spring-back amount of theblank (B) having the average plate thickness and the average materialconstants is calculated to be 2.0°, the pinching-in angle for bending bya predetermined angle of 90° is 88°.

For the other blanks (A) and (C), the finishing angles when they arebent to the pinching-in angles similar to the calculated pinching-inangle 88° of the blank (B) are obtained from the spring-back amountscalculated based on the individual actual plate thickness and materialconstants. As a result, since the spring-back amount and the finishingangle of the blank (A) are respectively 2.5° and 90.5°, the bendingerror is 0.5°. Since the spring-back amount and the finishing angle ofthe blank (C) are respectively 1.5° and 89.5°, the bending error is 0.5°(step S5 thus far).

For the foregoing three types of errors, i.e., the elongation error ofeach blank, the bending error of each blank under D value control, andthe bending error of each blank under pinching-in angle control,allowable ranges are set (step S6).

A message as to how much an actual error is deviated from the allowablerange, and which blank has the error within the allowable range isdisplayed on the not shown display unit of the control unit 19, forexample as shown in FIG. 13 (step S7).

Referring to FIG. 7, whether each of the above-described errors iswithin the allowable range or not is determined by each of the followingdetermination units of the control unit 19 (step S8).

Regarding the “elongation error”, the elongation error determinationunit 63 determines whether an “elongation error” of each blank is withinthe allowable range or not.

In the case of the blank having the “elongation error” outside theallowable range, the blank is bent such that a significant dimensionpart of the blank is set to a predetermined dimension. For example, inorder to pass up the elongation error to the other flange, thesignificant dimension part is first bent (step S9). Alternatively, inthe case of the blank having an “elongation error” outside the allowablerange, no bending work is carried out (step S10).

In the case of the blank having an “elongation error” within theallowable range, normal bending work is carried out at the press brake 5(step S11).

Regarding the “D value control bending error”, the D value bending errordetermination unit 65 determines whether the “D value control bendingerror” of each blank is within the allowable range or not.

In the case of the blank having the “D value control bending error”outside the allowable range, an alarm is displayed to an operator. Inthis case, the operator calculates the D value (stroke amount) withrespect to a predetermined angle based on the individual actual platethickness and material constants of each blank. Accordingly, sincebending is carried out at the press brake 5 by using the D value strokeamount with respect to the predetermined angle, the finishing angle issurely set within the allowable range (step S9). Alternatively, in thecase of the blank having the “D value control bending error” outside theallowable range, no bending work is carried out (step S10).

In the case of the blank having the “D value control bending error”within the allowable range, normal bending work is carried out at thepress brake 5 by the D value based on the average plate thickness andthe average material constants (step S11).

Regarding the “pinching-in angle control bending error”, the pinching-inangle bending error determination unit 67 determines whether the“pinching-in angle control bending error” of each blank is within theallowable range or not.

In the case of the blank having the “pinching-in angle control bendingerror” outside the allowable range, as in the case of theabove-described D value control, the spring-back amount is obtainedbased on the actual plate thickness and the material constants of eachblank, and the pinching-in angle with respect to a predetermined angleis calculated based on this spring-back amount. Accordingly, sincebending work is carried out at the press brake 5 by using thepinching-in angle with respect to the predetermined angle, the finishingangle is surely set within the allowable range (step S9). Alternatively,in the case of the blank having the “pinching-in angle control bendingerror” outside the allowable range, no bending work is carried out (stepS10).

In the case of the blank having the “pinching-in angle control bendingerror” within the allowable range, normal bending work is carried out atthe press brake 5 (step S11).

As described above, the actual plate thickness and the actual materialconstants of each blank are measured during punching in blanking workbefore bending, and this measurement information is reflected onbending. Thus, efficient and accurate bending is carried out. Moreover,for example, a block of blanks having small bending errors simplifieswork in the inspection time. Thus, the inspection time after bending isshortened.

Next, description will be made of another plate material processingmethod using the plate material processing system of the foregoingconfiguration according to a second embodiment. Explanation of portionssimilar to those of the first embodiment is omitted.

The second embodiment is different from the first embodiment in that fordetection of the actual plate thickness distribution and the actualmaterial constant distribution of a work W, these are obtained at theturret punch press 3 during blanking by punching of each blank in thefirst embodiment, while they are obtained during trial-punching at wasteholes in the second embodiment, and blanking is carried out after thedetermination as to whether each of the foregoing bending errors iswithin the allowable range or not.

Referring to FIG. 14, steps S21 and S22 are similar to steps S1 and S2in FIG. 7.

For the work W, as shown in FIG. 15, a blank layout is decided for eachblank, and waste holes 133 of trial-punching for plate informationmeasurement are positioned among the blanks (step S23).

A processing program containing development data of the waste holes 133for trial-punching and each blank on the work W is transmitted to thecontrol unit 19 of the turret punch press 3. At the turret punch press3, as shown in FIG. 16, the waste holes 133 are subjected to actualpunching based on the processing program. However, each blank is notpunched.

At the plate thickness/material constant detection unit 39 of thecontrol unit 19, the plate thickness and the material constants such asa tensile strength in each punching position are calculated duringpunching of each waste hole 133. Thus, as shown in FIG. 9, an actualplate thickness distribution and an actual material constantdistribution of the work W are calculated. This processing issubstantially similar to step S3 of the first embodiment shown in FIG.7.

Therefore, the actual plate thickness and the material constants of eachblank are decided from the above-described plate thickness and materialconstant distributions (step S24).

Among the blanks, a particular blank having the average plate thicknessand the average tensile strength is extracted as in the case of step S4of the first embodiment shown in FIG. 7. Alternatively, as shown in FIG.17, a test piece to be crushed is decided (step S25).

Then, at the control unit 19, at least one of three bending errors,i.e., an “elongation error”, a “D value control bending error”, and a“pinching-in angle control bending error” is predicted based on theabove-described actual plate thickness and material constants of eachblank.

The “elongation error” is now explained more in detail. At the platethickness/material constant detection unit 39 of the control unit 19, anelongation value of each blank is calculated based on the actual platethickness and the actual material constants of each blank. On the otherhand, the “average elongation value” is calculated based on the actualplate thickness and the actual material constants of the blank havingthe average plate thickness and the average material constants among theblanks. A difference between this average elongation value and theactual elongation value of each blank becomes the “elongation error”.

The “D value control bending error” and the “pinching-in angle controlbending error” are similar to those in step S5 of the first embodimentshown in FIG. 7 (step S26).

Steps S27 and S28 are similar to steps S6 and S7 of FIG. 7.

Referring to FIG. 14, whether each of the above-described errors iswithin the allowable range or not is determined by each of the followingdetermination units of the control unit 19 (step S29).

Regarding the “elongation error”, the elongation error determinationunit 63 determines whether the “elongation error” of each blank iswithin the allowable range or not.

In the case of the blank having the “elongation error” outside theallowable range, at the automatic programming machine 1 or the like, andeveloped dimension is calculated again by the elongation valuecalculated based on the actual plate thickness and the actual materialconstants of each blank (step S30). Alternatively, in the case of theblank having the “elongation error” outside the allowable range, nobending work is carried out (step S31).

In the case of the blank having an “elongation error” within theallowable range, at the automatic programming machine 1 or the like, adeveloped dimension is calculated based on the elongation value of theblank having the average plate thickness and the average materialconstants or the test piece (step S32).

Then, at the turret punch press 3, each blank is punched and subjectedto blanking based on the developed dimension of steps S30 and S32 (stepS33).

Each blank is bent at the press brake 5 (step S34).

That is, regarding the “D value control bending error” and the“pinching-in angle control bending error”, determination is made as towhether the “D value control bending error” or the “pinching-in anglecontrol bending error” of each blank is within the allowable range ornot, and then bending work similar to that in step S9 or S11 of thefirst embodiment is carried out.

Alternatively, in the case of the blank having the “D value controlbending error” and the “pinching-in angle control bending error” outsidethe allowable range, no bending work is carried out (step S31).

As described above, the actual plate thickness distribution and theactual material constant distribution of the work are measured duringtrial-punching before bending. Thus, the actual plate thickness and theactual material constants of each blank are decided, and thismeasurement information is reflected on accurate development andblanking of each blank. Since the measurement information is alsoreflected on bending, efficient and accurate bending is carried out.Moreover, for example, a block of blanks having small bending errorssimplifies work in the inspection time. Thus, the inspection time afterbending is shortened.

In the foregoing embodiment, the calculation of the bending error or thelike is carried out in the control unit of the punching machine.However, the calculation may be carried out by other computers through anetwork or the like.

Generally, sheet metal processing accuracy includes dimensional accuracyin punching, dimensional accuracy in cutting width, and bending angleaccuracy. In order to obtain high bending angle accuracy thereamong, askill of a highest level is required. For the purpose of reducing thisskill requirement, various bending angle detectors, mechanisms or thelike have been developed.

However, in the case of the conventional sheet metal processing system,for carrying out highly accurate bending satisfying the above-describedneed, necessity of a conventionally practiced trial-bending step hasbeen a problem.

The following embodiment has been made to solve such a problem, and itis designed in brief to eliminate the necessity of trial-bending orreduce the number of trial-bending times by detecting beforehand a trueplate thickness or a true spring-back amount of each blank to be bentbeforehand in blanking step.

Referring to FIG. 18, at a sheet metal processing system 201, as agenerally used blank processing machine, a punch press such as a turretpunch press 203, a laser processing machine, or a punch lasercombination processing machine is used. The blank processing machineincludes a work characteristic detection unit loaded to detect a platethickness of the work W and a spring-back amount during bending.

Thus, at the blank processing machine, punching and laser cutting areexecuted to carry out blanking and, simultaneously, plate thicknessmeasurement and spring-back amount detection are carried out by the workcharacteristic detection unit. Then, in a next bending step by thebending machine, such as a press brake 205, data of the above-describedplate thickness and spring-back amount is used as a control parameter,and thus the hitherto practiced trial-bending step is made unnecessary.That is, since the material characteristics of the work W, e.g., atensile strength σ, a work hardening coefficient C and the like, areobtained based on the data of the plate thickness and the spring-backamount, the obtained material characteristics are used in bending.

A basic idea of the present invention is as follows. To carry out highlyaccurate bending, in bending work using the press brake 205, it isnecessary to control positioning of a movable table in such a way as toset the following while the work W is interposed between dies:Control target bending angle α=drawing designated angle θ+spring-backangle ε.

Moreover, to reach the drawing designated angle θ with high accuracy, itis necessary to clearly set conditions of a die dimension including adie V groove width dimension, a die shoulder radius and a punch tipradius, and the material characteristics including the plate thicknesst, and the tensile strength σ. The plate thickness t has a relation ofsquare, and the tensile strength σ has a strong correlation.

Similarly, as conditions for understanding the spring-back angle ε, itis necessary to clearly set material characteristics including thetarget bending angle θ, the plate thickness t, the work hardeningcoefficient C, an index n, and elastic modulus, and the die dimensionincluding the punch tip radius. Then, a relation of σ=Cεn is set betweenthe work hardening coefficient C and the index n.

The die dimension is uniquely decided when the model number of the dieto be used in bending is clarified.

As apparent from the foregoing, in order to accurately obtain a drawingdesignated angle θ, it is only necessary to understand the platethickness t and the tensile strength equivalent value (numerical valuerepresenting tensile strength) of the work W, each having a strongcorrelation with each angle.

Thus, since the spring-back angle ε has a strong correlation with thetensile strength σ, a measured value of the spring-back angle ε can beapplied to the condition for obtaining the highly accurate drawingdesignated angle θ. In other words, in the present invention, thespring-back angle ε is treated as the numerical value representing thetensile strength σ of the work W.

In addition, as widely known, even if same control is executed, anglesafter removal of a bending force are different from each other betweenbending parallel to a rolling direction and bending in a perpendiculardirection. A main cause of this may be a difference in tensile strengthσ between the respective directions. Accordingly, in any directions, toobtain a highly accurate bending angle, it is necessary to understandnumerical values (material characteristic values) representingindividual tensile strengths of the directions parallel andperpendicular to the rolling direction, and separately use these inbending.

Based on the foregoing, at the sheet metal processing system 201 of thepresent invention, first, the plate thickness t of a member (includinglater-described sample) as a blank is measured. Then, blank processingsuch as punching or laser cutting is carried out. Directly in the sameclamping state, bending parallel and bending perpendicular to a rollingdirection of the sample are carried out by, for example a bending angleof 90°. Then, the spring-back amount ε is measured at the sample bent by90° for each of the foregoing bending, and the measured value is storedas the material characteristic values in a control unit 207 of the blankprocessing machine. Thereafter, such material characteristic values arereferred to in bending using the press brake 205.

That is, at the control unit 209 of the press brake 205, the materialcharacteristic values are received from the control unit 207 of theblank processing machine, and control for positioning the movable tableis executed by incorporating the material characteristic values in abending angle control algorithm. For example, the actually measuredplate thickness t is directly used, and the tensile strength equivalentvalues are separately used for each bending direction(parallel/perpendicular to rolling direction). Accordingly, it ispossible to highly accurately obtain a target angle from firstprocessing without executing trial-bending.

By referring to FIG. 18, explanation is now made of the embodiment usingthe blank processing machine, for example the turret punch press 203.

The turret punch press 203 is a known press and, in brief, it is formedin a frame structure, where both sides of an upper frame 215 aresupported on side frames 213 erected in both sides of a base 211. On thelower portion of the upper frame 215, a disk-shaped upper turret 217including a variety of punches P to be freely detached and exchanged isrotatably loaded. A lower turret 219 facing the upper turret 217 isrotatably loaded on an upper surface of the base 211. This lower turret219 includes a number of dies D facing the variety of punches P, and thedies D are disposed in a circular-arc shape and loaded to be freelydetached and exchanged. Shaft centers of the upper and lower turrets 217and 219 are disposed on the same shaft center. The upper and lowerturrets 217 and 219 are rotated in synchronization in the same directionby control of the control unit 207.

By rotations of the upper and lower turrets 217 and 219, desired punch Pand die D are indexed and positioned below a ram 221 (punch pressmember) located in a processing position.

The turret punch press 203 also includes a work movement positioningdevice 225 for moving a plate-shaped work W placed on a processing table223 back and forth, and left and right, and positioning it to theprocessing position. The work movement positioning device 225 includes acarriage base 227 provided on the right end of the processing table 223in FIG. 18 so as to be freely moved in a Y axis direction. On thiscarriage base 227, a carriage 231 including a plurality of work clamps229 for claming the work W is provided so as to be freely moved in an Xaxis direction. The work movement positioning device 225 is controlledby the control unit 207.

In the control unit 207, an input unit 235 such as a keyboard, and adisplay unit 237 such as a CRT are connected to a central processingunit, for example a CPU 233. By operating the input unit 235 and thedisplay unit 237, a three-dimensional drawing, a development drawing orthe like of a product is made, and a processing program for deciding away of processing is prepared, and then stored in a memory 239. Based onthis processing program, punching of the turret punch press 203 iscontrolled.

Thus, based on the processing program of the control unit 207, the workW is set in a processing position by the work movement positioningdevice 225, and then the punch P is struck by the ram 221. Thus, thework W is subjected to punching by cooperation between the punch P andthe die D. Accordingly, for example a blank 241 shown in FIG. 19 isobtained.

Referring to FIG. 19, for example, a sample A as a sample is used forobtaining the spring-back amount ε in bending parallel to a rollingdirection in FIG. 19. For example, a sample B as a sample is used forobtaining the spring-back amount ε in bending perpendicular to therolling direction.

The blanks A and B are developed shapes of products and, by bendingparts (C and D) indicated by dotted lines in the drawing, final productshapes (boxes in the example) are obtained. As shown in FIG. 20, thesamples A and B are both in microjoint states and, in these states, thesamples are bent by 90°. The blanks A and B are similarly in microjointstates.

The micro-joint has only a very small effect on the bending anglebecause its width is equal to/lower than 0.2 mm. Accordingly, thespring-back amount ε substantially equal to that in the case of no jointis obtained. The spring-back amount ε obtained in bending of the sampleA is referred to when the C part shown in FIG. 19 is bent by using thepress brake 205, and similarly the sample D is referred to when the Dpart is bent.

As described above, one of the features of the present embodiment isthat the samples (two types of parallel/perpendicular) for the purposeof detecting spring-back amounts ε are processed in the same step as theprocessing of the blanks.

Next, description will be made of the work characteristic detection unitconstituting a main portion of the embodiment, for example a measuringunit 243. This measuring unit 243 can detect the spring-back amount εand measure the plate thickness.

Referring to FIGS. 21 and 22, the measuring unit 243 can be divided intotwo modules, i.e., a probe module and a die module. In the embodiment,the former is incorporated in the upper turret 217 of the turret punchpress 203, and the latter into the lower turret 219. However, both maybe combined to constitute a single device. In this case, the device maybe installed in any positions within a range, where the work W can besubjected to positioning control, and the device is effective when it isinstalled in the laser processing machine or the punch laser combinationmachine.

The probe unit 245 is made of probe members, for example a probe 247 anda sensor plate 249. The probe 247 is equivalent to a punch die inbending. When the ram 221 is lowered, the probe 247 itself is loweredthrough a striker 251. Bending is carried out by interposing the work Wbetween the probe 247 and the die 253. A displacement amount of the ram221 can be detected by position detecting means loaded on another notshown member.

The sensor plate 249 has a structure to be moved up and down relative tothe probe 247, and is always pressed downward by a spring 255 so as tobe protruded downward by a predetermined length (x1 in the embodiment)from a lower end of the probe 247. In addition, an upper end of thesensor plate 249 can be detected by a photoswitch 257 loaded on anothernot-shown member, and a displacement amount of the sensor plate 249 canbe detected by a position sensor 259 in FIG. 21. The photoswitch 257 andthe position sensor 259 are connected to the CPU 233 of the control unit207.

Next, description will be made of a series of plate thickness detectionand spring-back detection operation carried out by using the measuringunit 243. The plate thickness detection and the spring-back amountdetection may be carried out as independent operations.

First, description is made of a principle of the plate thicknessdetection according to the embodiment.

Referring to FIGS. 21 and 22, as the probe unit 245 is graduallylowered, a tip of the sensor plate 249 is first bumped into the work W,for example a surface of the sample, and subsequently a tip of the probe247 is bumped into the work W. During this period, as indicated by (1)in FIG. 24, the sensor plate 249 is raised by a displacement amount x1relative to the probe 247, and the tip of the probe 247 is set in thestate of being bumped. That is, in the state that vertical positions ofthe tips of the probe 247 and the sensor plate 249 coincide with eachother (S point in FIG. 24), the photo switch 257 is turned on.

The probe unit 245 is lowered and pressed to a reference plate havingthe plate thickness clarified beforehand, i.e., the reference platethickness t1, a position of the probe unit 245 when the photoswitch 257is turned on is read by the position sensor 259 and stored in the memory239.

The probe unit 245 is positioned on a bending line of the sample and, atthe time of starting bending of the sample, the probe unit 245 is passedthrough (1) in FIG. 24, and pressed to the sample as described above,and a position t2 of the ram 221 when the photoswitch 257 is turned onat the point S in FIG. 24 is detected. At this point of time, a measuredplate thickness of a blank 241 is obtained by a plate thicknessarithmetic unit 261 based on an equation, i.e., measured platethickness=reference plate thickness t1+(t1−t2). Here, (t1−t2) representsan actual plate thickness error with respect to the reference platethickness. A shown in FIG. 18, the plate thickness arithmetic unit 261is electrically connected to the CPU 233 of the control unit 207.

Next, description is made of a detection principle of the spring-backamount according to the embodiment.

With the lowering movement of the ram 221, the probe 247 is continuouslylowered, and thus bending work is carried out. In this case, adisplacement amount of the sensor plate 249 is shifted from (2) to (3)in FIG. 24.

Then, as shown in FIG. 23A, when the sample reaches a position of atargeted bending angle θ1 (θ1=90° in the embodiment) by the probe 247,the displacement amount of the sensor plate 249 is detected by theposition sensor 259, and stored in the memory 239. At this time, leftand right face angles a and b (a and b in FIG. 21) of the sensor plate249 are in contact with an inner surface of the bent sample.

Subsequently, when the ram 221 is raised to also raise the probe 247 inorder to remove a bending load, a bending angle θ2 of the sample iswidened by spring-back as shown in FIG. 23B. Accordingly, the sensorplate 249 is set in a lowered state as indicated by (5) in FIG. 24.During this period, the left and right angles (a and b in FIG. 23) ofthe sensor plate 249 are always in contact with the inner surface of thesample.

When the spring-back is finished, and the lowering of the sensor plate249 is stopped, the displacement amount of the sensor plate 249 isdetected by the position sensor 259. Then, a difference in detectionvalues by the position sensor 259 before and after the spring-back iscalculated by a spring-back arithmetic unit 263. If this displacementamount is x2, then this value becomes equivalent to the spring-backamount (spring-back equivalent value). As shown in FIG. 18, thespring-back arithmetic unit 263 is electrically connected to the CPU 233of the control unit 207.

In addition, the probe unit 245 is raised when the detection of thedisplacement amount x2 is finished as indicated by (6) in FIG. 24.

Next, explanation is now made of the embodiment using the bendingmachine, for example the press brake 5.

By referring to FIG. 18, since the press bake 5 is publicly known one,schematic explanation is made. The press brake 205 of the embodimenttargets a hydraulic down stroking press brake. However, an up strokingpress brake or a mechanical press brake using a crank other than thehydraulic type may be used.

The hydraulic down stroking press brake 205 has a punch P loaded andfixed on a lower surface of a movable table freely moved up and down,for example the upper table 265 through a plurality of intermediateplates 267. A die D is loaded and fixed on an upper surface of a fixingtable, for example a lower table 269. Accordingly, the work W as a platematerial is bent between the punch P and the die D by cooperationthereof.

In FIG. 19, left and right shaft hydraulic cylinders 275 and 277 areinstalled above left and right side frames 271 and 273 constituting amain body frame. The upper table 267 as a ram is connected to lower endsof piston rods 279 of the left and right shaft hydraulic cylinders 275and 277. The lower table 269 is fixed on the lower portion of the leftand right side frames 271 and 273.

The press brake 205 includes a control unit 209 such as an NC controlunit. In the control unit 209, bending condition input means such as aninput unit 283 for entering data such as the material of the work W, theplate thickness, a processing shape, a die condition, the target bendingangle, and the processing program, a display unit 285 such as a CRT, anda memory 287 for storing such entered data, or the materialcharacteristic data such as the plate thickness or a spring-back amountobtained by the turret punch press 203 are connected to a centralprocessing unit, for example a CPU 281.

A bending program file 289 prepared by fetching the materialcharacteristic data in a control algorithm is also connected to the CPU281.

A D value arithmetic unit 291 for preparing a ram control value (Dvalue) based on the material characteristic data or other data such asdie information is connected to the CPU 281. At this D value arithmeticunit 291, a predetermined angle may not be achieved when bending iscarried out by a different punch P and a different die D loaded on thepress brake 205 using the spring-back value detected based on the punchP and the die D on the blank processing machine side. Thus, at the pressbrake 205 side, the D value is subjected to correction when processingis carried out by the punch P and the die D different from those on theblank processing machine.

Next, description is made of a standard process at the sheet metalprocessing system 201 according to the embodiment.

In the blank processing machine, for example the turret punch press 203,when blank processing is started, first, the work W is positioned in anattachment position of the measuring unit 243. The plate thickness ismeasured by using the measuring unit 243. In FIG. 19, the platethickness is measured for each of the samples A and B and the blanks Aand B. Instead of measuring the plate thickness for all the samples Aand B and the blanks A and B, one the plate thickness of therepresentative sample or blank may be measured.

Subsequently, an outer periphery of each member, i.e., the samples A andB and the blanks A and B is cut. In this case, each member is joined bymicrojoints.

At a stage when the cutting is finished, the sample is positioned againto be set directly under the measuring unit 243. In this state, forexample bending of 90° is executed, and a spring-back amount ε at thistime is measured. Similar operations are performed for both of thesamples A and B, and two types of spring-back amounts ε of bendingparallel to and perpendicular to a rolling direction of the material areextracted.

The plate thickness and the spring-back amount ε thus measured, and thedie condition used for bending are stored in the memory 239 of thecontrol unit 207 in, for example an array similar to that shown in FIG.25. If a product bending line includes any one of bending lines parallelto and perpendicular to the rolling direction, the spring-back amount εis measured only for the sample A or B having such a bending line.

Then, at a stage where punching/cutting is finished, the members asproducts, e.g., the blanks A and B shown in FIG. 19, are separated fromthe work W, and the process proceeds to bending using the press brake205. In this bending work, in order to obtain a target angle from firstbending, array data similar to that shown in FIG. 25, which has beenstored in the memory 239 of the control unit 207 of the turret punchpress 203, must be fetched in the bending control algorithm of the pressbrake 205. In this case, two methods are conceivable for passing thearray data to the control unit 209 of the press brake 205.

One is a method of executing direct marking by printing a mark orpasting a bar code label on the blank 241. As a type of marking, atwo-dimensional barcode or a QR code which has frequently been used canbe used. For marking processing, a general commercial item can be used.For example, an ink jet unit is available in the case of printing, and alabel printer or the like is available in the case of label pasting.

In such a case, the mark is linked with the above described array databeforehand and, at the time of starting bending by the press brake 5, acode is read by using, for example a commercially available barcodereader. Accordingly, the linked array data can be extracted. Thereafter,this array data is transmitted from the memory 239 of the control unit207 of the turret punch press 203, incorporated in the bending controlalgorithm of the bending program file 289 of the control unit 209 of thepress brake 205, and bending control is executed.

Another is a method of using a data communication line. The array datacollected by using the measuring unit 243 is stored in the control unit207 through the communication line and, at the time of starting bendingby the press brake 205, the array data is directly fetched in thecontrol unit 209 of the press brake 205 through the communication line.Accordingly, thereafter, the bending control similar to the foregoing isexecuted.

The blank 241 obtained at the turret punch press 3 is subjected tobending by the press brake 205 in the next step. Thus, at the controlunit 207 of the turret punch press 203, as shown in FIG. 18, the data istransmitted to the control unit 209 of the press brake 205.

The present invention is not limited to the described embodiments and,by proper changes, the present invention can be executed in other mode.

In the described embodiments, the detection operation using themeasuring unit 243 was described. However, the detection operation canbe carried out by combining a well-known bending angle detector and awell-known plate thickness detector.

INDUSTRIAL APPLICABILITY

As can be understood from the foregoing description of the embodimentsof the present invention, the actual plate thickness and the actualmaterial constants of each blank can be efficiently and accuratelymeasured during punching in blanking before bending. Thus, this measuredinformation can be reflected on bending, and efficient and accuratebending can be carried out.

The actual plate thickness and the actual material constants of eachblank can be measured during punching in blanking before bending. Thus,this measured information can be reflected on bending, and efficient andaccurate bending can be carried out. Moreover, for example, a block ofblanks having small bending errors simplifies work in the inspectiontime. Thus, the inspection time after bending can be shortened.

The elongation error of each blank can be measured beforehand. Thus,since bending along an actual situation can be carried out depending onwhether the elongation error is within the allowable range or not, it ispossible to improve product accuracy and work efficiency during bending,and shorten the inspection time after bending.

Since the actual plate thickness distribution and the actual materialconstant distribution of a work can be measured during trial-punchingbefore bending, the actual plate thickness and the actual materialconstants of each blank can be decided. Since this measured informationcan be reflected on accurate development and blanking of each blank, andalso reflected on bending, efficient and accurate bending can be carriedout. Moreover, for example since a block of blanks having small bendingerrors simplifies work in the inspection time, it is possible to shortenthe inspection time after bending.

Since the elongation error of each blank can be calculated beforehand,bending along an actual situation can be carried out depending onwhether the elongation error is within the allowable range or not. Thus,it is possible to improve product accuracy and work efficiency duringbending, and shorten the inspection time after bending.

Since the bending error under control of a stroke amount of each blankcan be calculated beforehand, blanking and bending along an actualsituation can be carried out depending on whether the bending error iswithin the allowable range or not. Thus, it is possible to improveproduct accuracy and work efficiency during bending, and shorten theinspection time after bending.

A bending error under control of a pinching-in angle of each blank canbe calculated beforehand. Thus, since blanking and bending along anactual situation can be carried out depending on whether the bendingerror is within the allowable range or not, it is possible to improveproduct accuracy, and work efficiency during bending, and shorten theinspection time after bending.

Since the actual plate thickness distribution and the actual materialconstant distribution of a work can be measured during punching beforebending, the actual plate thickness and the actual material constants ofeach blank can be decided. Since this measured information can bereflected on accurate development and blanking of each blank, and alsoreflected on bending, efficient and accurate bending can be carried out.Moreover, for example since a block of blanks having small bendingerrors simplifies work in the inspection time, it is possible to shortenthe inspection time after bending.

Since an elongation error of each blank can be calculated beforehand,bending along an actual situation can be carried out depending onwhether the elongation error is thin the allowable range or not. Thus,it is possible to improve product accuracy, and work efficiency duringbending, and shorten the inspection time after bending.

Since the elongation error of each blank can be calculated beforehand,bending along an actual situation can be carried out depending onwhether the elongation error is within the allowable range or not. Thus,it is possible to improve product accuracy and work efficiency duringbending, and shorten the inspection time after bending.

Since the bending error under control of the stroke amount of each blankcan be calculated beforehand, blanking and bending along the actualsituation can be carried out depending on whether the bending error iswithin the allowable range or not. Thus, it is possible to improveproduct accuracy and work efficiency during bending, and shorten theinspection time after bending.

Since the bending error under control of the pinching-in angle of eachblank can be calculated beforehand, blanking and bending along an actualsituation are carried out depending on whether the bending error iswithin the allowable range or not. Thus, it is possible to improveproduct accuracy and work efficiency during bending, and shorten theinspection time after bending.

In the blank processing step such as punching or laser cutting beforethe bending step, at least one of the plate thickness and thespring-back amount of the work is detected as quantitative data of thematerial characteristic necessary for bending simultaneously with blankprocessing. Since at least one of the plate thickness and thespring-back amount of the work is incorporated as a control parameter inbending control at a stage of bending using the press brake, it ispossible to obtain a bent product having a target angle from firstbending without carrying out trial bending.

At the blank processing machine carrying out punching or laser cuttingin the step before bending, at least one of the plate thickness and thespring-back amount of the work is detected as quantitative data of amaterial characteristic necessary for bending simultaneously with blankprocessing. Thus, since at least one of the plate thickness and thespring-back amount of the work is incorporated as the control parameterin the bending control at a stage of bending using the press brake, itis possible to obtain a product having a target bending angle from firstprocessing without carrying out trial bending.

At the blank processing machine, at least one of the plate thickness andthe spring-back amount of the work can be detected as quantitative dataof a material characteristic necessary for bending simultaneously withblank processing before bending. Thus, it is possible to use at leastone of the plate thickness and the spring-back amount of the work as acontrol parameter at the stage of bending.

The probe member is lowered to the work set in a predetermined position,and the sensor plate is brought into contact with the work. Then, whenthe probe member is brought into contact with the work while the sensorplate is in contact with the work, tips of the probe member and thesensor plate coincide with each other. It is possible to easily andaccurately calculate the plate thickness of each of the sample and theblank based on a difference between the measured position informationdetected by position detecting means at this time and the referenceposition information detected by the position detecting means when thetips of the probe and the sensor plate coincide with each other inprevious measurement of a known reference plate thickness.

It is possible to easily and accurately calculate the spring-back amountof the sample based on a difference between the bending positioninformation detected by the position detecting means when the probemember is lowered by a predetermined stroke to bend the sample and thespring-back position information detected by the position detectingmeans when the probe member is separated form the sample, and the sampleis sprung back.

At the work plate thickness measuring device, the probe member islowered to the work set in a predetermined position, and the sensorplate is brought into contact with the work. Then, when the probe memberis brought into contact with the work while the sensor plate is incontact with the work, tips of the probe member and the sensor platecoincide with each other. It is possible to easily and accuratelycalculate the plate thickness of each of the sample and the blank basedon the measuring position information detected by the position detectingmeans at this time and the reference position information detected bythe position detecting means when the tips of the probe and the sensorplate coincide with each other in previous measurement of a knownreference plate thickness.

At the spring-back measuring device, it is possible to easily andaccurately calculate the spring-back amount of the sample based on adifference between the bending position information detected by theposition detecting means when the probe member is lowered by apredetermined stroke to bend the sample and the spring-back positioninformation detected by the position detecting means when the probemember is separated from the sample and the sample is sprung back.

1. A method for processing a plate material, the method comprising:punching a work into a plurality of blanks, based on a nominal platethickness and a nominal material constant of the work, while detecting aram stroke and a pressure at each punching of the work into blanks;calculating an actual plate-thickness distribution and an actualmaterial-constant distribution of the work, based on data of the ramstrokes and the pressures detected in the punching of the work intoblanks; and determining an actual plate thickness and an actual materialconstant of each blank based on the actual plate-thickness distributionand the actual material-constant distribution of the work.
 2. The methodaccording to claim 1, further comprising: bending each blank, based onthe determined actual plate thicknesses and actual material constants.3. The method according to claim 2, wherein, in the bending of eachblank, an elongation value of the blank is calculated based on thedetermined actual plate thickness and the actual material constant ofthe blank being bent, wherein a determination is made as to whether adifference between the calculated elongation value and a nominalelongation value, obtained based on a nominal plate thickness and anominal material constant of the work, is within an allowable range,wherein, when the difference is within the allowable range, the bendingis based on the actual plate thickness and the actual material constant,and wherein, when the difference is outside the allowable range, thebending is stopped or a significant part is subjected to bending basedon the actual plate thickness and the actual material constant.
 4. Themethod according to claim 2, wherein the bending of each blank comprisescalculating an average stroke amount for an average blank, having anaverage plate thickness and average material constant, that is bent by apredetermined angle, wherein a determination is made as to whether abend angle is within an allowable range of the predetermined angle whenanother blank is bent by the calculated stroke amount, wherein, when thebend angle is within the allowable range, the blank is subjected tobending by the calculated stroke amount, and wherein, when the bendangle is outside the allowable range, the bending is stopped or theblank is subjected to bending by another stroke amount calculated basedon the actual plate thickness and the actual material constant.
 5. Amethod for processing a plate material according to claim 2, wherein thebending of each blank comprises calculating an average pinching-in anglefor an average blank having an average plate thickness and averagematerial constant by obtaining a spring-back amount for the averageblank, wherein a determination is made as to whether a finishing angleis within an allowable range when another blank is bent by thecalculated pinching-in angle, wherein, when the finishing angle iswithin the allowable range, the blank is subjected to bending by thecalculated pinching-in angle, wherein, when the finishing angle isoutside the allowable range, the obtained spring-back amount is utilizedto calculate another pinching-in angle based on the actual platethickness and the actual material constant, and bending is carried outusing the other calculated pinching-in angle.
 6. A method for processinga plate material prior to punching a work into a plurality of blanks,the method comprising: trial-punching in gaps between adjoining blanks,based on a nominal plate thickness and a nominal material constant ofthe work, while detecting a ram stroke and a pressure at eachtrial-punching in the gaps; calculating an actual plate-thicknessdistribution and an actual material-constant distribution of the work,based on data of the ram strokes and the pressures detected in thetrial-punching; determining an actual plate thickness and an actualmaterial constant of each blank based on the actual plate-thicknessdistribution and the actual material-constant distribution of the work;blanking each blank by punching the work into the plurality of blanks,based on the determined actual plate thicknesses and actual materialconstants; and bending each blank, based on the determined actual platethicknesses and actual material constants.
 7. The method according toclaim 6, wherein, in the blanking of each blank, an elongation value ofthe blank is calculated based on the determined actual plate thicknessand actual material constant of the blank being blanked, wherein adetermination is made as to whether a difference between the calculatedelongation value and an average elongation value, based upon an averageblank having an average plate thickness and average material constant,is within an allowable range, wherein, when the difference is within theallowable range, the blank is subjected to blanking based on the averageplate thickness and the average material constant, and wherein, when thedifference is outside the allowable range, the blanking is stopped orthe blank is subjected to blanking based on the actual plate thicknessand the actual material constant.
 8. The method according to claim 6,wherein the bending of each blank comprises calculating an averagestroke amount for an average blank, having an average plate thicknessand average material constant, that is bent by a predetermined angle,wherein a determination is made as to whether a bend angle is within anallowable range of the predetermined angle when another blank is bent bythe calculated stroke amount, wherein, when the bend angle is within theallowable range, the blank is subjected to bending by the calculatedstroke amount, and wherein, when the bend angle is outside the allowablerange, the bending is stopped or the blank is subjected to bending byanother stroke amount calculated based on the actual plate thickness andthe actual material constant.
 9. The method according to claim 6,wherein the bending of each blank comprises calculating an averagepinching-in angle for an average blank, having an average platethickness and average material constant, by obtaining a spring-backamount for the average blank, wherein a determination is made as towhether a finishing angle is within an allowable range when anotherblank is bent by the calculated pinching-in angle, wherein, when thefinishing angle is within the allowable range, the blank is subjected tobending by the calculated pinching-in angle, and wherein, when thefinishing angle is outside the allowable range, the obtained spring-backamount is utilized to calculate another pinching-in angle based on theactual plate thickness and the actual material constant of the blankbeing bent, and bending is carried out using the other calculatedpinching-in angle.
 10. A system for processing a plate material,comprising: an automatic programming machine that calculates an expandeddimension of a blank, based on a nominal plate thickness and a nominalmaterial constant of a work to be processed; a punching machine thatpunches the work into a plurality of blanks by cooperation of a punchwith a die while detecting a ram stroke and a pressure at each punchingof the work into blanks; a control unit including a platethickness/material constant arithmetic unit that calculates an actualplate-thickness distribution and an actual material-constantdistribution of the work based on data of the ram strokes and thepressures detected in the punching of the work into blanks, and thatdetermines an actual plate thickness and an actual material constant ofeach blank based on the actual plate-thickness distribution and theactual material-constant distribution of the work, and a bending machinethat bends each blank, based on the determined actual plate thicknessand the actual material constant of the blank being bent.
 11. The systemfor processing a plate material according to claim 10, wherein thecontrol unit includes an elongation error determiner that determineswhether a difference between an elongation value of each blank,calculated based on the determined actual plate thickness and the actualmaterial constant of the blank being bent, and a nominal elongationvalue, obtained based on a nominal plate thickness and nominal materialconstant of the work, is within an allowable range.
 12. The system forprocessing a plate material according to claim 10, wherein the controlunit includes an elongation error determiner that determines whether adifference between an elongation value of each blank, calculated basedon the determined actual plate thickness and the actual materialconstant of the blank being bent, and an average elongation value, basedupon an average blank having an average plate thickness and averagematerial constant, is within an allowable range.
 13. The system forprocessing a plate material according to claim 10, wherein the controlunit includes a stroke control bending error calculator that calculatesan average stroke amount for an average blank having an average platethickness and average material constant, and that determines whether abend angle is within an allowable range of a predetermined angle whenanother blank is bent by the calculated stroke amount.
 14. A system forprocessing a plate material according to claim 10, wherein the controlunit includes a pinching-in angle control bending error determiner thatcalculates a pinching-in angle by obtaining an average spring-backamount for an average blank having an average plate thickness andaverage material constant, and that determines whether a finishing angleis within an allowable range when another blank is bent by thecalculated pinching-in angle.